On the edge of a terraced mountainside in the Himalayan foothills, a Nepalese soldier watches through tears as villagers crowd aid trucks bringing blankets.

Ang Jon Sherpa was sent to the Dolakha district, 180 kilometres east of Nepal's capital Kathmandu on the China border, to ensure supplies are not looted.

But he is thinking about his baby daughter – last seen three days ago, when a magnitude-7.3 aftershock unleashed a second wave of destruction across the landlocked country, little over two weeks after it was first hit by a massive earthquake on April 25.

"We were running, and rocks came falling on us," he said.

"My daughter died but I'm here doing my duty. I never stopped working."

Duty aside, Jon said he simply could not afford to stop; having received no aid and needing to rebuild his home, destroyed in the first quake, at the same time as his military paycheque of 15,000 rupees ($184) a month was docked by half, the rest diverted to aid.

Relief has been widely criticised for coming too slowly, and not at all to many in Nepal.

Three weeks after the earthquake, isolated villages high up in the Himalayas near China have yet to be reached, and hundreds of thousands of people are living without a roof over their heads.

The death toll from the magnitude-7.8 quake and aftershocks has risen above 8,500, injuring 20,000 people, and wrecking more than half a million houses. Bodies are still being pulled from the rubble.

The United Nations is now warning of "real potential for more deaths", if aid does not get to those living scattered across the mountainous terrain before the annual monsoon – expected in three weeks.

Some people might be able to walk the two days it takes to get to an aid point but they're not going to be able to bring it back at scale to help their whole village

Caroline Anning from Save The Children's

After this, tracks wash away, mountainsides shaken by tremors will sheer off in landslides, and many in the hardest areas to reach will be cut off.

"Have we gotten in touch with everyone? No, I would be lying if I said we had, but every day we are significantly expanding our outreach," said Leszek Barczak, public information officer for the UN Office for the Coordination of Humanitarian Affairs.

The challenge is that while aid has been sent to the 14 most affected districts, within those, 240,000 people cannot be reached by road and 75,000 are beyond even where helicopters can land.

"I've seen the way they live, actually, using donkeys and baskets that they put on their back to bring stuff up and down," Mr Barczak said.

Race to deliver aid before weather turns

Aid workers are under pressure to get supplies to the unreachable areas before the monsoon waylays logistics.

At the moment relief aid is being flown to agreed spots, with communities told when and where to pick it up via radio and text message. Even now, non-government organisations know this will not work for everyone.

"Some people might be able to walk the two days it takes to get to an aid point but they're not going to be able to bring it back at scale to help their whole village," said Caroline Anning, from Save The Children's emergency response team.

She said those least able to get it, single mothers and the elderly, were also most vulnerable to the cold and disease they run the risk of exposure to should they not receive any.

To try and get around this, aid agencies are using walking teams and employing mountain climbing porters to haul up supplies.

But time is running out, with thunderclouds already starting to scud across the Kathmandu Valley.

"If we start getting landsides and we start getting roads flooding, like what happened a few days ago in Chautara [district], that basically doubles the amount of people we cannot access," Mr Barczak said.

It also makes operations vastly more expensive, with more helicopters needed.

Meanwhile the UN's appeal for $US425 million is drastically underfunded, with just 14 per cent received. Logistics only has 24 per cent of what is needed to get aid out.

All of which, the UN says, has "serious implications".

Houses wiped out in some northern villages

In Dolakha, a winding six-hour drive from Kathmandu, it is easy to see why people are worried.

Three days after the May 12 aftershock, with its epicentre in the district, rescue helicopters whomp circles in the sky.

If you go to the northern areas now, that are the poorest and more inaccessible, you're looking at 100 per cent uninhabitable houses.

Plan International field manager Dualta Roughneen

The only vehicles weaving around rubble spewed across the street from collapsed buildings belong to aid workers and military.

The aftershock killed at least 154 people, wrecked 96 per cent of the houses, and sent landslides ripping down the mountains, cutting off roads.

"Which means we're more kilometres away from the areas we previously couldn't reach," said Dualta Roughneen, Plan International field manager, sitting on the porch of a resort acting as a makeshift base for aid workers.

"If you go to the northern areas now, that are the poorest and more inaccessible, you're looking at 100 per cent uninhabitable houses."

And just 20 per cent of the "less accessible areas" have received aid.

Corruption, politics hampering aid response

Just a month before the quake, Britain's International Development Committee called for the British parliament to cut its aid program to combat corruption in Nepal.

Some volunteers working on quake relief have reported that customs officials have been demanding bribes to allow aid across from India.

That is not the only obstruction: Red tape bottlenecks at Nepal's only international airport have been cleared, with customs fees now waived, but there is still a backlog of planes waiting to fly in, according to Ms Anning from Save The Children.

Nepal's government – which has been preoccupied with writing a constitution since its monarchy was abolished eight years ago – was criticised for not acting fast enough initially.

No government, no authority, no country can truly prepare for a disaster of this magnitude.

Leszek Barczak from the UN Office for the Coordination of Humanitarian Affairs

Then it was accused of trying to wrest control of relief, demanding donations be channelled into the Prime Minister's Disaster Relief Fund, while promising free hospital treatment, and compensation payments for those people with dead relatives and damaged homes.

Nepal's government has yet to release a detailed relief action plan which was promised in a motion tabled in parliament May 9.

But it is not far off now, according to Tirtha Raj Bhattarai, secretary of Kathmandu's district disaster relief committee.

Headed by the chief district officer (CDO), the committee is responsible for steering relief on the ground.

With the district administration office declared unsafe due to quake damage, Mr Bhattaraj and his team work under a white tarpaulin tent erected in the courtyard outside.

Mr Bhattaraj smiles, mentioning that he brushed shoulders with Nepal's prime minister Sushil Koirala when their draft disaster relief plan was handed over on May 15.

"We made our suggestions and the government is drafting [the details]," he said.

"Within a short time they will deliver the procedures and they will deliver money," after which, he predicts the CDO will swing into action, building shelters for tens of thousands homeless across Kathmandu.